436 



The Ohio Journal of Scie?ice [Vol. XIX, No. 8, 



The animals inhabiting the area are given in Table 3, below. 

 There is a marked decrease in the number of species found 

 here as compared with the list in Table 2. Most of the reduc- 

 tions come in the coleoptera; only two species of these were 

 found, both of them adults. The absence of the surface beetles 

 such as the gyrinids, so abundant at the opposite end of the pond, 

 was noticeable and is apparently to be correlated with the great 

 amount of filamentous algae present, the mat it formed clearly 

 making locomotion difficult. The Notonecta were also scarce 

 and in this instance, likewise, the algce probably offered a 

 hindrance to their free locomotion. i 



TABLE 3. 



The figures in the table refer to the number of individuals found in an area 12 by 18 inches. 



The thirty-four snails listed as coming from the stones beyond 

 the littoral zone include some from the algae. Here again the 

 young snails were mostly in the algae and the larger ones among 

 the stones near the bottom. 



Station 4. This station included the west side of the pond. 

 It is shown on page 437. The floor of the quarry in this region 

 gradually sloped beneath the water so that the depth of water 

 was from a fraction of an inch along the edge to four or five 

 inches fifty feet from shore. In the shallowest water there was 

 practically no vegetation. In deeper water there were some 

 filamentous algae. On the bottom there were a few millimeters 

 of organic sediment and also a few stones, most of them small. 



